Project Summary While studies support the efficacy of comprehensive, school-wide interventions in reducing bullying, these types of programs can require significant time and financial resources for implementation, resulting in barriers to providing school-based bullying prevention, especially in low-income and rural communities. Additionally, although training bystanders to act as ?defenders? on behalf of targets of bullying is an important intervention component, few programs include this as part of their comprehensive strategy. Brief programs that focus on bystander training and require fewer resources are needed to reduce bullying and its negative consequences. The PI (Dr. Midgett) developed STAC, a brief, stand-alone bullying bystander intervention for middle school students, to reduce bullying and mental health risks for bystanders. Brief, in-person programs, however, still pose implementation barrier such as training school personnel, providing external support, and not allowing for large groups of students to be trained at the same time. For this project, we propose to develop a technology- based STAC intervention (STAC-T) that will allow students to customize their experience by selecting avatars and bullying scenarios based on our previous studies conducted in a range of middle schools, including those in low-income and rural communities. We will also incorporate an assessment and personalized feedback component to promote behavior change. The innovative, user-centered design proposed will be inherently sensitive to cultural needs of students and identify personally-appropriate strategies. The specific aims of this application include conducting a needs analysis to determine product need, building a system prototype leveraging our prior work and expertise of an external advisory board, and usability and effectiveness testing with middle school students and stakeholders to evaluate feasibility. This proposal is designed to document proof of concept and finalizing design and content of the system which will be developed and tested in a subsequent randomized clinical trial. The technology-based platform will increase the overall reach, impact, and sustainability of the STAC intervention for bullying prevention. It will substantially reduce cost to increase reach and its interactivity and algorithms can tailor program content to adapt it further for students attending low-income and rural schools. Thus, this low-cost, easy to disseminate technology-based bullying bystander intervention has the potential to have a substantial impact on the problem of bullying and the negative associated consequences for both students who are targets and bystanders in middle school when the problem of bullying peaks. There is a large market for the STAC-T intervention with approximately 100,000 public and private schools with middle-school grades in the United States. Globally, the online education market is growing at 10% a year and the digital health market exceeds $220 billion annually.